Nitrosoanilinonitroalkanes



United States Patent 3,151,161 NI'IROSOANILINONITROALKANES Darrell D. Mullins, Nitro, and Lloyd A. Walker, St.

Albans, W. Va., assignors to Monsanto Qhemical Company, St. Louis, Mo., a corporation of Delaware N0 Drawing. Filed Jan. 9, 1961, Ser. No. 81,243 8 Claims. (Cl. 260-577) The present invention relates to nitrosoanilinonitroalkanes, to methods for their preparation and to promoting reaction of vulcanizable elastomers and reinforcing pigment by means of nitrosoanilinonitroalkanes.

It has long been known that rubbers may be altered by thermal treatment of an admixture with a relatively high proportion of reinforcing pigment, usually carbon black. The time required for external treatment may be materially shortened by carrying out the thermal interaction in the presence of organic catalysts or promoters. However, the alteration in properties is neither uniform nor necessarily even advantageous. Chemicals which catalyze the thermal treatment of one rubber may be severely detrimental to another. Some catalysts active in natural rubber proved inert in less saturated rubber like butyl rubber. Others useful for improving the hysteresis properties of butyl rubber gave little or no benefit with the more unsaturated rubbers and caused objectionable side reactions, as for example cross linking. The action of catalysts for low hysteresis processing has been explained on the basis of promoting reaction between rubber and carbon black. While the improved adjuvants provided by the present invention are presumed to function by similar mechanisms and are therefore described as promoters, this is not really known. The invention is not limited to any theory of the mechanism by which the new compounds impart the desirable properties hereinafter described in detail.

An object of the invention is to provide new chemicals which promote the low hysteresis of rubber vulcanizates. A general object of the invention is to improve the properties of natural and synthetic rubbers by means of special treating agents. Another object is to provide agents which increase the modulus, lower the torsional hysteresis and' decrease the internal friction of rubber vulcanizates. A specific object is to promote reaction between rubber and carbon black or other reinforcing pigment by organic chemical catalysts. A further object is to provide promoters uniformly effective in rubber-carbon black mixtures. A further specific object is to improve dispersion of carbon black and other fillers in rubber.

Improved vulcanizates are obtained according to the present invention by incorporating into the rubber mixture a relatively large amount of reinforcing pigment, a small amount of a nitrosoanilinonitroalkane as hereinafter disclosed in detail and heating the mixture. Amounts of 0.15.0% of the rubber hydrocarbon comprise the practical useful range under most conditions. These are not the absolute limits and measurable effects are obtained with even smaller amounts. Similarly, larger amounts can be used but usually without advantage. The preferred range is 0.2S-1.0%. Vulcanizing and other ingredients as desired are added, preferably after mixing rubber, reinforcing pigment and promoter. Any vulcanizing ingredients present during thermal interaction must be present in amounts below those which cause cure. In general, heat treatment can be carried out in an oven without mechanical agitation of the mixture.

Another method is by heat treating the rubber mixture, reinforcing pigment and nitrosoanilinonitroalkane while subjecting it to mechanical agitation as in a Banbury mixer or on a mill. Heating is preferably within the range of 300370 F. with heating times ranging from one minute to 16 hours. It is desirable to pre-heat the Banbury to at least 300 F. before charging the rubber and catalyst. The heat of mixing even with full cooling raises the temperature 20 to 40 degrees higher depending upon the initial temperature. The process can be completed in a normal mixing cycle after which. vulcanizing ingredients are added. For plant scale operation short mixing cycles are desired.

Any of the rubber reinforcing pigments may be used in the practice of the present invention. These include reinforcing silica but carbon blacks are preferred. The amount and type of carbon black can be varied within wide limits. Usually it will be in the range of 25 to of the rubber and normally 40-50 parts by weight in the case of tread stocks. Carbon black is generally added first in the mixing cycle and in the usual practice of the invention the promoter is added concomitantly with it. On the other hand, the promoter may be premixed with the carbon black and the mixture added to rubber. Alternatively, rubber and promoter are admixed followed by the carbon black and other ingredients as desired. However, the thermal treatment must be conducted in the presence of reinforcing pigment. Banbury mixing is advantageous because it exerts severe masticating action and achieves uniform dispersion of the ingredients within short mixing times. The dispersing action of the new compounds is pronounced.

The nitrosoanilinonitroalkanes of this invention con tain a nitro substituent beta to the amino nitrogen, a methylene group attached to nitrogen and a nitroso substituent in the para position of the anilino radical. All three structural features are critical. For example, corresponding compounds lacking either the nitro or nitroso radical or in which the methylene group is replaced by methyl substituted methylene are in general inactive for promoting reaction of butyl rubber and carbon black. Surprisingly, the nitro substituent increases thermal stability of the molecule. Nitrosoanilinonitroalkanes of this invention possess the general formula a R2 i R is hydrogen or lower alkyl or taken together R and R are alkylene. R and R preferably are not hydrogen. R is hydrogen, lower alkyl or nitroso and R is hydrogen, halogen, or alkyl. These compounds form readily in high yields from simple raw materials. They are preferably made by synthesizing the corresponding N-nitroalkyl aniline as described by Johnson in Jour. Am. Chem. Soc., 68, 14-18 (1946), and treating the resulting product with a nitrosating agent.

3 The following examples are illustrative but not limitative of the preparation of the new compounds.

Example 1 To 32 grams (0.137 mole) of N-(l-nitrocyclohexylmethyl)aniline in 200 ml. of isopropyl alcohol at 2530 C. was added dropwise in 10 minutes 16.4 grams (0.16 mole) of concentrated hydrochloric acid. The mixture was then cooled to 25 C. and a solution of 10 grams (0.137 mole) of 98% sodium nitrite in 25 ml. of water added dropwise in 10 minutes at 2530 C. The reaction mixture was stirred at this temperature for an hour, cooled to 5 C. and the solid collected by filtration. The precipitate was washed with water until free of chlorides and air dried at room temperature to yield 34 grams of product. After recrystallization from dilute acetone solution it melted at 110111 C. To 26.3 grams (0.1 mole) of the N-(l-nitrocyclohexylmethyl)-N-nitrosoaniline thus prepared in 200 ml. of acetic acid was added dropwise with stirring at 25-30 C. 100 grams (1.0 mole) of concentrated hydrochloric acid. After the addition, which required 30 minutes, the reaction was stirred at 2530 C. for 3 hours, added to 2000 ml. of ice-water and pH ad-. justed to 8 by addition of concentrated ammonium hydroxide. After stirring for 30 minutes, the solid was collected by filtration, washed with water until free of chlorides and air dried at room temperature. N-(l-nitrocyclohexylmethyl)-p-nitrosoaniline was obtained in 100%. yield as a light green solid. After recrystallization from ethyl alcohol it melted at 142-143 C. Analysis gave 15.83% nitrogen compared to 15.96% calculated for 13 l7 3 3- Example 2 To a stirred mixture of 31.5 grams (0.174 mole) of N-(2-nitropropyl)aniline and 200 ml. of glacial acetic acid at 25-30 C. was added dropwise in minutes 31 grams (0.31 mole) of concentrated hydrochloric acid. To the resulting slurry was added slowly by means of a powder funnel in 5 minutes 12.5 grams (0.174 mole) of finely divided 97% sodium nitrite. After stirring for 30 minutes at 25-30 C., 100 grams (1.0 mole) of concentrated hydrochloric acid was added dropwise to the reaction mixture over a period of 30 minutes. Stirring was continued for 3 hours at 25-30 C. after which time the reaction was discharged into 2500 ml. of ice-water and neutralized to a pH of 8 with concentrated ammonium hydroxide. After stirring for 30 minutes, the dark green solid was removed by filtration, Washed with water and air dried at room temperature. N-(Z-nitropropyl)-p-nitrosoaniline was obtained in 74.3% yield melting at 121- 124 C.

' Example 3 A mixture of 37 grams (0.144 mole) of 3-chloro-N-(2- methyl-Z-nitropropyl)aniline and 200 ml. of glacial acetic acid was heated to a maximum temperature of 40 C. to form a solution. The solution was then cooled to 25 C. and 17.3 grams (0.173 mole) of concentrated hydrochloric acid added dropwise at 2530 C. over a period of 5 minutes. Then at this same temperature range 10.3 grams (0.144 mole) of 97% sodium nitrite dissolved in ml. of Water was added dropwise at 30 C. over a period of 15 minutes. The reaction mixture was stirred for 3 hours at 25-30 C., warmed to 35 C., stirred for an additional hour and then discharged into 2500 ml. of ice-water. Concentrated ammonium hydroxide was then added until a pH of 8 was reached. After stirring for minutes, the product was removed by filtration, washed with water and air dried at room temperature. 3-chloro- N-(2-methyl-2-nitropropyl)-4-nitrosoaniline was obtained as a light green solid melting at 106-109 C. after recrystallization from methyl alcohol. Analysis gave 16.87% nitrogen compared to 16.31% calculated for C10H12C1N303.

4 Example 4 To 350 grams of a 41% solution of methyl alcohol and hydrochloric acid at 0-5 C. was added dropwise in 20 minutes 76.5 grams (0.37 mole) of N-(2-methyl-2-nitropropyl)-N-methylaniline. After standing for 10 minutes, 27 grams (0.37 mole) of sodium nitrite was added in one portion. After removing external cooling, the temperature rose to 35 C. in 25 minutes. The reaction mixture was stirred for 4 hours at 2535 C., discharged into 2500 ml. of ice-water and isolated as described above. N-(2- methyl-2-nitropropyl)-p-nitroso-N-methylaniline was obtained as a brown solid in 40% yield. After recrystallization from ethyl alcohol it was a bright green solid melting at 1245-1265 C. Analysis gave 17.62% nitrogen compared to 17.71% calculated for C I-1 N 0 Example 5 To a stirred mixture of 74 grams (0.382 mole) of N-(2- nitrobutyl) aniline and 200 ml. of glacial acetic acid at 25- 30 C. was added dropwise over a 10 minute period 46 grams (0.46 mole) of concentrated hydrochloric acid. To the resultant slurry at 2530 C. was added slowly by means of a powder funnel in 10 minutes 27.2 grams (0.382 mole) of finely divided, 97% sodium nitrite. The reaction mixture was stirred for an additional 30 minutes at this temperature range, cooled to 25 C. and 200 grams (2.0 moles) of concentrated hydrochloric acid added dropwise over a 45 minute period. Stirring was continued for 3 hours at 25-30 C., the solid collected by filtration and washed with ether. The dry salt cake was discharged into 2500 ml. of ice-water, neutralized to a pH of 8 with concentrated ammonium hydroxide and stirred for 30 minutes. The green solid was removed by filtration, washed with cold water until the washings were neutral to litmus and air dried at room temperature. N-(Z-nitrobutyl)-p-nitrosoaniline was obtained melting at 100.5 101.5 C. after recrystallization from ethyl alcohol. Analysis gave 18.72% nitrogen compared to 18.83% calculated for C10H13N303.

Example 6 To a stirred mixture of 33.4 grams (0.15 mole) of N- (Z-methyl-Z-nitropropyl)-4-nitrosoaniline and 200 ml. of glacial acetic acid at 1020 C. was added dropwise in 10 minutes 20 grams (0.2 mole) of concentrated hydrochloric acid. To the resultant slurry at Ill-20 C. was added dropwise in 10 minutes 11 grams (0.15 mole) of 97% sodium nitrite dissolved in 35 ml. of water. The reaction mixture was stirred for minutes at 2530 C., filtered and washed free of chlorides with Water. The N,4-dinitroso-N-(2-methyl-2-nitropropyl)aniline was ob tained in 81.5% yield. After recrystallization from ethyl alcohol the green crystals melted at 9091 C. Analysis gave 21.84% nitrogen compared to 22.18% calculated for 10 12 4 4- Example 7 A mixture of 38.8 grams (0.2 mole) of N-(Z-methyl- 2-nitropropyl)aniline and 200 ml. of glacial acetic acid was heated to 35 C. to form a solution. The solution was then cooled to 25 C. and 25 grams (0.25 mole) of concentrated hydrochloric acid added dropwise at 25- 30 C. over a period of 10 minutes. After stirring the thick slurry at 2530 C. for 10 minutes, 16 grams (0.23 mole) of 97% sodium nitrite dissolved in 25 ml. of water was added dropwise at 2530 C. over a period of 30 minutes. Stirring was continued at 25-30 C. for 30 minutes, after which time grams (1.5 moles) of concentrated hydrochloric acid was added dropwise at 25-30 C. in 30 minutes. The resulting mixture was stirred at 2530 C. for 3 hours, the solid removed by filtration and Washed with ethyl ether. The dry salt cake was then added to 2500 ml. of ice-water and concentrated ammonium hydroxide added at 015 C. until a pH of 8 had been reached. After stirring for 1 hour at -20" C., the resulting solid was removed by filtration, washed with water until the washings were neutral to litmus and air dried. There was obtained a green solid in 58.5% yield. The N-(Z-methyl-Z-nitropropyl)-p-nitroreturned on torsional deformation. One-half the logarithmic decrement of the observed amplitude was recorded. Heat rise from the base temperature after flexing in a Goodrich flexometer at 212 F. was also detersoaniline, melting at l31l32 C., analyzed 18.36% nitro- 5 mined. Typical results are recorded below: gen compared to 18.83% calculated for C H N O A yield of 96.5% was obtained employing 100 m1. of I 300% Torsional Heat methyl alcohol as the solvent and 55 grams (1.51 moles) 01191111021 Addltwe Modulus 5 5 of anhydrous hydrogen chloride. After recrystallization from ethyl alcohol, the product melted at 131132 C. 10 h h fi t h t h 3,238 8.58 2 1 r r Example 8 N-e-niii iiuighp m iigi ihat? 2,520 0.092 is A mixture of 34.3; grams 0.1 mole) of N,N-dinitro 'g3iitiiigiihifiiiii flft fi ffitfll.. 2,260 0.097 20 so N,N diphenyl 2 methyl 2 nitro 1,3 propane- N-Methyl-N hl-methyl-Z-nitropropyD- 2 diamine and 350 ml. of glacial acetic acid was heated to $figi jfifg g g i mg;"" I540 @086 18 40 C. The near solution which resulted was then cooled i e- 3,040 8 9 to 25 C. and 200 grams (2.0 moles) of concentrated if"3i ;g g l ff K: 2620 M88 19 hydrochloric acid added dropwise at 2530 C. over a period of 30 minutes. The cooling means was then ren H f If h h d moved and stirring continued for three hours. The maxi- 1 6 a 3uvants especia y u ccmpoun mum temperature reached during this period was 33 C. mg blends of natural and B cop9lymer i The complete solution obtained was divided into two Due to the poorer hysteresls PYOPFTFES of tne synthetlc as equal parts and each Part was poured into 2590, m1 of compared to the natural product, it 1s not feasible to make and neutrahmd to a PH of 8 with concentrated thick articles subject to severe stress, as for example large ammonium hydroxide. The neutralized mixtures were truck P rubber- EXCeSSWe heat then stirred for minutes and the solid products filtered, stimulates durmg use ca usmg early fa11ure- However, for Washed with water and air dried at room temperature. reams of economy i Common to admlx natural bis(p nhmsophgnyl) 2 methyl 2 nhm ber -wrth the synthetic product but the amount of synpropanediamine was obtained as a light green solid meltthet1c fvh1ch can used depends P the hysteresls ing at l42.3 C. after washing with hot ethyl alcohol. The 30 Propefltms of i h Pmctics of the f m yield was 965% of Product analyzing 19 86% nitrogen invention permits the use or higher amounts of synthetic compared to 20 39% calculated for C16H17N5O4 than would otherwise be feasible. As illustrative of the As illustrative of the desirable properties imparted to advantages Obtamed from bknds of rubbers: a mlXtuT? of rubber compositions by thg mew adj-Wants: examples 70 parts natural rubber and 3O parts styrene-bntadrene thereof were added along with carbon black and styrene- COPOll/mer rabbi/{treated Wlth Carbon black and P butadiene copolyrner rubber to a Banbury mixer. SBR miner was Compamd to natur a1 mbbgr f The 1500 rubber 1400 parts by weight, was charged to the mlxturet 140.0 Parts by f Was Charged a Baflbllry Bahbury mhger and mixed for 3 minutes at The mixer and mixed for 5 minutes at 77 F. The chemical to test material was then added to a portion, 400 parts by tested was then added to a 400 Parts by Weight P weight, of the rubber from the Banbury mixer. The addi- 40 non the rubber from the fi on H1111 tion was made on the differential rolls of a rubber mill at 158 Stock abouh 5 mlnutes at F The Stock was mined for about 5 minutes and out several tlmes from side to side to obtarn adequate and out several times from side to side to obtain adequate dlsPerslon' The mllled P ti n Cohtammg the test madispersion The mined portion Containing the test mate, terlal was then added to the remainder of the stock in rial was then added to the remainder of the stock in the the Banbufy mixer whether i a b a k- The In1X- Banbury to ether with carbon black. The Banbury mixer er was heaied to 302 making these addltloilswas to F. before making these additions Banbury mixing was continued for a total of six minutes Banbury mixing was continued for a total of 6 minutes and stoclfs than Z p and P F F at 212 F. and the stocks then dumped and passed six time? through aruboer at The 31113111111811!- hmes through a rubber n at R Vukanizable gredrents were added on the mill at 158 The natural stocks were compounded on the mill at 122 F. by addrubber qontwkwas Prepared by ngflsiwatms the rpbber ing stearic acid, zinc oxide, hydrocarbon oil softener, sulthree minutes In a Banbury at 77 The mastlcated fur, antioxidant and accelerator. These were then comrubber and black then added t0 & l pared to a similarly prepared stock without the chemical Banbury at 302 and f f for three mmlltes, the additive. The completed formulations were as follows: lf Swept down and l contmued for another three minutes. The composition was then transferred to Parts byweight a rubber mill at 158 F. and passed six times through a the mill. Remaining ingredients were added on the mill. Stock A B The final compositions were as follows:

SBR 1500 100 100 Parts by weight Chemical adding/eh "56" 58. 5 55332123? (I A 4 4 Stock o D n F Stearic acid 2 2 h r i i""i1""i Tr u i 5 i 5 Natural rubber 100 1 1 i rarrune a l i-giti igi it gd-abegggg iia ofisiil eriziriridc 1.2 1.2 Natural rubher-SBR(/30) 100 100 100 Sulfur 1. 1. 75 N -(l-N rtrocyclohexylmethyl)-pnitrosoaniline 0.5

N-( 2t-Methyll-2-uitropropyD-p- 0 5 The stocks were cured in the usual manner by heating in 111 q q me ,4-D t, -2- th 12- t a press 45 minutes at 291.2" F. The modulus of elastrcme y m m 5 ity at 300% elongation was determined in the usual man- 70 gf ggi g g 2 2 2 ner. Torsional hysteresis was determined at r m Stearicacid:: III 3 2.7 2.1 2.7 perature with an apparatus which embodied a torsional Egg?e%gg gg ih ggi g 3 5 5 5 pendulum. In this apparatus the sample of rubber tested fenm'nide 71 Q71 M1 supplied the force to restore the pendulum when it was Sulfur deflected. This supplied a measure of the energy not 75 300% Ult. Mooney Torsional Stock Modulus Elong. Scorch Hysteresis at 121 C A mixture of equal parts by weight of natural rubber and SBR copolymer rubber treated with carbon black and promoter was compared to a natural rubber control. A mixture of equal parts natural and SBR copolymer rubber was blended for three minutes in a Banbury mixer at 77 F. The promoter was mixed with 700 grams of carbon black by thorough shaking in a large bottle. The carbon black and promoter mixture together with 1400 grams of the rubber mixture from the first step were added to a pre-heated Banbury mixer at 212 F. The composition was masticated for three minutes, the Banbury swept down and mastication continued for another three minutes. The composition was then transferred to a rubber mill at 158 F. and passed six times through themill. Remaining ingredients were then added on the mill. The natural rubber control was prepared as in the previous natural rubber-8BR copolymer blend. Further demonstration of the invention Was carried out employing a stock with a promoter concentration of 0.25 part. The completed formulations were as follows:

erties of butyl rubber. Butyl rubber-carbon black compositions comprising Parts by weight Stock1- K L Butyl rubber (a copolymer. of 97.5% isobutylene and 2.5% isoprene) 100 100 Carbon black (super abras n furna 26 26 N-(2-Methyl-2-nitropropyl)-p-nitroso 0. 5

were prepared in a Banbury mixer preheated to a temperature of 284 F. After heating and mixing the compositions for five minutes there was added Zinc oxide 1. 5 5 Stearic acid 1 1 Hydrocarbon oil softener 10 10 Carbon black (super abrasion furnace) 14 14 Tellurium diethyldithiocarbamate 1 1 2,2- Dithiobis(bcnzothiazole) 1 1 Sulfur 0. 75 0.75

The stocks Were vulcanized by heating 45 minutes at 307 F. and physical properties tested with the results recorded below:

Stock 300% Torsional Parts by weight Modulus Hysteresis 40 Stock t. G H J K 690 0.175 L 950 0136 Natural rubber 100 Natural rubber-8BR (50/50). 100 100 ohemical romoter w 8-5 8- Butyl rubber which is a copolymer of at least 85% ggggg g ff igi y isobutylene and a small amount, not more than 15%, of ste ric ae]i3d .1 1 f t g g-g diolefin, as for example isoprene, butadiene or piperylene, gy xggfi ggf l ig gfig ijfiffififififij' is normally deficient in resilience and the foregoing data diamina-. fl hh n n 115 demonstrate that new compounds of this invention may 05 85 Q85 be used advantageously to improve resilience. The opti- Sulfur 5 mum amount will depend upon the particular stock used.

The stocks were cured in the usual manner by heating in a press for 45 minutes at 291.2" F. The resulting properties are recorded below:

300% Torsional Mooney Stock Modulus Hysteresis Scorch at 240.8 F.

Parts by weight Stock N Butyl rubber Channel black (EPC) Furnace black (HAF) N1- (2Methyl-2-nitropropyD-a-nitrosQanime Zinc oxide 5 Tetramethylthluram disulfide 1 2,2-Dithiobis(benzothiazole) 1 Sulfur 2 vulcanization was carried out by heating in a press for 45 minutes at a temperature of 307 F. The vulcanizates were then tested and the results obtained are shown below:

These data demonstrate increasing resilience as the dosage of catalyst is increased. Improvement in resilience is independent of the curing system used. Decreasing the sulfur and accelerator levels lowered the modulus but torsional hysteresis was not significantly changed. Comparable improvements in resilience are obtained with other curing systems following heat treatment promoted by the new compounds, as for example peroxide curing agents, quinone dioxime curing agents and dinitrosobenzene. Also, it will be appreciated that the new compounds have obvious utility as intermediates. They are useful for preparation of complex amines by reduction of the nitroso and nitro radicals.

It is intended to cover all changes and modifications of the examples of the invention herein chosen for purposes of disclosure which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

1. A compound possessing the formula R3 r NO2?CH2N NO where R is selected from the group consisting of hydrogen, lower alkyl,

and

R is selected from the group consisting of hydrogen and lower alkyl and taken together with the carbon to which they are attached R and R represent lower cycloalkyl, R is selected from the group consisting of hydrogen, lower alkyl and nitroso and R is selected from the group consisting of hydrogen, chlorine and alkyl.

2. A compound possessing the formula where R and R are lower alkyl, R is hydrogen and R is chlorine.

3. A compound possessing the formula N on R where R and R are lower alkyl and R is hydrogen.

4. A compound possessing the formula N on R: R H, i m

i. where R and R are lower alkyl and R is nitroso.

5. A compound possessing the formula where R and R are lower alkyl and R is methyl.

6. A compound possessing the formula NO: R2

where R is lower alkyl and R is hydrogen. 7. A compound possessing the formula H 0%, 1oH,-NN0

CHg-Cg 8. A compound possessing the formula H NOr-'(l]CHzNNO References Cited in the file of this patent UNITED STATES PATENTS 420,311 Poirrier Ian. 28, 1890 2,495,774 Roberts Jan. 31,1950 2,623,024 Barton Dec. 23, 1952 2,710,287 Barton et a1. June 7, 1955 

1. A COMPOUND POSSESSING THE FORMULA 